Recently, in order to fill minute interconnection trenches or via holes defined in a surface of a substrate, it has been customary to use a substrate processing apparatus (plating apparatus) for plating a substrate such as a semiconductor substrate with a metal such as copper, which has a smaller electric specific resistance than aluminum or aluminum-based materials, to form embedded interconnections in the trenches or via holes.
FIG. 1 is a schematic view showing a conventional arrangement of a facedown plating apparatus. As shown in FIG. 1, the conventional facedown plating apparatus comprises an upwardly opened cylindrical plating bath 312 for holding a plating liquid 310 therein, and a head 314 for detachably holding a substrate W such as a semiconductor substrate thereon in such a state that a surface of the substrate W faces downwardly. The head 314 is positioned so as to cover an upper opened end of the plating bath 312. In the plating bath 312, a flat anode plate 316 is horizontally disposed and immersed in the plating liquid 310. The anode plate 316 serves as an anode electrode. The substrate W held by the head 314 has a peripheral edge connected to a cathode electrode via an electrode contact provided on the head 314. The anode plate 316 is made of a porous material or a mesh-like material.
A center of a bottom in the plating bath 312 is connected to a plating liquid ejection pipe 318 for forming an upward flow of the plating liquid in the plating bath 312. An upper portion of the plating bath 312 is surrounded by a plating liquid reservoir 320 for receiving plating liquid that has overflowed the plating bath 312. The plating liquid ejection pipe 318 is connected to a plating liquid supply pipe 328 extending from a plating liquid regulating tank 322. The plating liquid supply pipe 328 has a pump 324 and a filter 326 connected thereto. The plating liquid regulating tank 322 is connected to a plating liquid return pipe 330 extending from the plating liquid reservoir 320.
The conventional plating apparatus operates as follows: The substrate W is held by the head 314 in such a state that the surface of the substrate W faces downwardly, and introduced downwardly into the plating bath 312 to be immersed in the plating liquid 310 in the plating bath 312. While a certain voltage is being applied between the anode plate 316 (anode electrode) and the substrate W (cathode electrode), the plating liquid in the plating liquid regulating tank 322 is ejected upwardly from the bottom of the plating bath 312 via the plating liquid ejection pipe 318 and applied as a jet vertically to a lower surface (a surface to be plated) of the substrate W. In this manner, a plated film is formed on the lower surface of the substrate W while a current is flowing between the anode plate 316 and the substrate W. The plating liquid 310 that has overflowed the plating bath 312 at this time is recovered by the plating liquid reservoir 320 and returned to the plating liquid regulating tank 322 via the plating liquid return pipe 330.
As described above, the substrate is immersed in the plating liquid in the plating bath. In a case where a peripheral edge of the substrate is connected to a cathode electrode provided on the head in a dry state, it is desirable that an electrode contact connected to the peripheral edge of the substrate be completely sealed from the plating liquid. Therefore, the electrode contact is sealed from the plating liquid by a sealing member. However, when a plating process is continuously performed, a residue of the plating liquid tends to be deposited and crystallized on the sealing member. This crystallized residue of the plating liquid on the sealing member is liable to reduce a sealing capability of the sealing member, resulting in deteriorated electric conduction between the substrate and the cathode electrode. Furthermore, immediately after the substrate has been plated, an oxide film is likely to be formed on the surface of the substrate by remaining plating liquid thereon. Therefore, after the substrate has been plated, the substrate and the sealing member need to be immediately cleaned with pure water or the like to replace the remaining plating liquid with pure water or the like.
In a conventional jet plating apparatus, a substrate to be plated is held horizontally and lowered into a plating bath to bring a lower surface of the substrate into contact with a surface (overflow surface) of plating liquid, and then further lowered until an entire lower surface of the substrate is immersed in the plating liquid. Therefore, when the substrate is immersed in the plating liquid, air bubbles tend to remain on the lower surface of the substrate because of downwardly overhung portions of components including an electrode contact and a sealing member, i.e., a substrate contact portion. These remaining air bubbles prevent a plated film from normally being formed on the surface of the substrate, and tend to produce defects such as voids in the plated film.